Quarter year The calendar year can be divided into four
quarters, often abbreviated as Q1, Q2, Q3, and Q4. Since they are three
months each, they are also called
trimesters. In the
Gregorian calendar: • First quarter, Q1: January 1 – March 31 (90 days or 91 days in leap years) • Second quarter, Q2: April 1 – June 30 (91 days) • Third quarter, Q3: July 1 – September 30 (92 days) • Fourth quarter, Q4: October 1 – December 31 (92 days) In some domains, weeks are preferred over months for scheduling and reporting, so they use quarters of exactly 13 weeks each, often following
ISO week date conventions. One in five to six years has a 53rd week which is usually appended to the last quarter. It is then 98 days instead of 91 days long, which complicates comparisons. In the
Chinese calendar, the quarters are traditionally associated with the 4
seasons of the year: •
Spring: 1st to 3rd month •
Summer: 4th to 6th month •
Autumn: 7th to 9th month •
Winter: 10th to 12th month
Quadrimester The calendar year can also be divided into three
quadrimesters (from French
quadrimestre), lasting for four months each. They can also be called the early, middle, or late parts of the year. In the
Gregorian calendar: • First quadrimester, early year: January 1 – April 30 (120 days or 121 days in leap years) • Second quadrimester, mid-year: May 1 – August 31 (123 days) • Third quadrimester, late year: September 1 – December 31 (122 days)
Semester The calendar year can also be divided into two
semesters, lasting six months each and often being abbreviated as S1 and S2. In the
Gregorian calendar: • First semester, S1: January 1 – June 30 (181 days or 182 days in leap years) • Second semester, S2: July 1 – December 31 (184 days) ==See also==